Acoustic device



INVENTOR.

mqga,

TORNEY.

Sept. 9, 1941. M TOMINAGA ACOUSTIC DEVICE Filed'May le, 1940 Patented Sept. 9, 1941 ACOUSTIC DEVICE Masaichi Tominaga, Hasunuma-cho, Kamataku, Tokyo, Japan Application May 16, 1940, Serial No. 335,631 In Japan September 22, 1939 2 Claims.

This invention relates to an acoustic device for arresting sounds at openings such as doorways or ventilators of the sound-arresting room, and it consists in the constructions, arrangements and combinations herein described and claimed. It is a particular object of the invention to provide a cylindroid-shaped sound-absorbing wall formed by a curved surface described by a circular, elliptic or parabolic line or by other secondary, tertiary or higher degree curved line which forms a focus positioned in the central part of each opening, having, on either side thereof, a soundabsorbing concave wall curved substantially parallel with the said cylindroid-shaped wall, and, at the upper ends of these walls, a sound-absorbing cupola.

The object of the invention is to completely arrest the sound and effect a smooth pass and ventilation from the sound-arresting room, by using curved sound-absorbing walls for sound-arresting purpose.

In the doorways of machinery rooms, trial rooms for motors or propellers, studios for talkies or other sound-arresting rooms in which noisy Sounders are accommodated, there have usually been employed in the past various constructions of sound-arresters, with the object of arresting the eiiluence of the sound outside the rooms, such as a sound-absorbing door, several sound-arresting barriers projected alternately from each side of the passage to the door in parallel with one another and at right angles to the passage, a cross sound-absorbing wall on cross passage, or the like. However, with barriers projected at right angles, the passage makes sharp turns, which not only causes a great inconvenience to tra-flic, but also, in case a strong sound accompanies rapid air current as in a trial of propellers, there is promoted in many instances a generation of sounds due to a sudden change of atmospheric pressure and in forming dense and rare parts in the air in consequence of a severe collision of the air current with the said wall at right angles. Besides, sounds may be generated by the air vortex produced in the rear of the wall. In `view of these faults, it is obvious that the old soundabsorbing wall arranged at right angles to the passage of sounds is not eicient.

The present invention, provides an apparatus for attaining the sound-arresting purpose smoothly and completely, having none of the abovementioned faults, in the passage of sounds, since a cylindroid-shaped sound-absorbing wall formed by a curved surface described by a circular, elliptic or parabolic line or by other secon- Lil 55 efficient.

dary, tertiary or higher degree curved line which forms a focus is provided in the central part of each opening, having, on either side of it, suitably spaced, a sound-absorbing wall curved substantially parallel with the said cylindroid-shaped wall, and, at their upper ends, a sound-absorbing cupola. Preferably the sound absorbing walls are constructed from plates comprising deer hair as their base, since these are found to be highly efficient in reducing sound.

The construction of the invention is illustrated in the accompanying drawing, in which Fig. 1 is a plan showing a horizontal section of the sound-arrester of cylindrical sound-absorbing walls used in the doorway and ventilator, according to the present invention. Fig. 2 is a sectional elevation along a line X-Y of Fig. 1. Fig. 3 is a section of a cylindroid-shaped soundabsorbing wall with wavy surface. Figs. 4 and 5 are sectional plans showing respectively cases applying ellipsoid and paraboloid sound-absorbing cylindroids to the present invention.

I indicates sound-arresting room, 2 is its outer wall and 3 shows sound-absorbing walls. The sound-arrester consists of a cylindrical soundabsorbing wall A having a diameter a little larger than the width of the doorway or ventilator. Curved sound-absorbing walls B and C are provided on either side of the Wall A almost parallel with it spaced at a distance almost equal to the wave-length of low-pitched sounds to be arrested, a sound-absorbing wall D at the exit and a soundabsorbing wall E at the cupola.

From the foregoing construction it will be apparent that sounds coming from the sound-arresting room I, are, as indicated by full and dotted lines, rst absorbed by the sound-absorbing wall of cylindroid-shaped curved surface and most sounds of short wavelength are thus quenched. The remaining sounds reflected from the surface are completely quenched by their being repeatedly reiiected and absorbed between the wall A and B or C. The sounds of long wave-length which are found most difficult of quenching, are

'd absorbed, after repeated reiiection between the said convex and concave surfaces, thereby making the reflected sound waves interfere with one another by the suiiicient phasic diii'erences created among the reflected waves. In the curved soundabsorbing vsurfaces having foci as in the present invention, sounds reflected from the central sound-absorbing cylindroid are always reilected back to the cylindroid, and as this action is continued sound absorption will be complete and Furthermore, that the sound-absorbof the doorway, just described, and the arrestingVV of sound is similarly accomplished.

In the present invention, as shown in Fig. 4, an elliptic cylindroid F and side sound-absorbing Walls G and H parallel with the cylindroid F can be used instead of using cylindrical forms, on the same principle as aforementioned. Also, as shown in Fig. 5, the uses of parabolically curved cylindroid L and side parabolic sound-absorbing surfaces M and N parallel to the cylindroid L are found to arrest sounds effectively. Furthermore, the uses of other curved surfaces formed by tertiary or higher degree curved lines with foci are all effective. When the sound-absorbing surfaces of the abovementioned cylindroids are undulating waved, jagged or grooved, as shown in Fig. 3, the area of the absorbing surfaces and the rate of absorption by interference are effectively increased. As the sound-arresting Walls according to the present invention are composed, as stated above, of curved lsurfaces arranged in parallel, it affords an advantage that persons can pass through the passage Way freely and air can smoothly pass between the Walls.

I claim:

1. A sound-arrester for the openings of a sound arresting room comprising a cylindroid-shaped sound-,absorbing Wall formed by a curved surface providing a focus in the pathway of sounds issuing from the openings, a sound-absorbing Wall substantially parallel with said cylindroid-shaped wall, and a sound-absorbing cupola enclosing the upper ends of said walls.

2. The structure of claim 1 in which said cylindroid-shaped Wall is provided with an undulating exterior surface.

MASAICHI TOMINAGA. 

